Elastic shaft coupling having a torsion element

ABSTRACT

The invention relates to an elastic shaft coupling having at least one torsion element ( 1 ) which comprises at least one elastomer body ( 5 ) serving as a transmission element. Axial metallic connecting flanges ( 2 ) are mounted in a fixed manner, preferably by vulcanization, on the input and output sides of the elastomer body. In order to increase the transmittable power density and to improve the rubber-metal connection in the edge areas of the connecting flanges ( 2 ), the invention provides that the connecting flanges ( 2 ) axially project outward with regard to the elastomer body ( 5 ) from the plane of the connecting flange while forming an arch at least on the radially extending edges ( 2   a   , 3   a ) of the connecting flanges between the elastomer body ( 5 ) and the connecting flanges ( 2 ), the edges being formed on the outer edges of connecting flange segments ( 2 ) and/or on the inner edges of passages ( 3 ) in the connecting flange ( 2 ). In addition, the elastomer body ( 5 ) is connected to the flanges by vulcanization along the arched area.

CROSS REFERENCE TO RELATED APPLICATIONS

Applicants claim priority under 35 U.S.C. §119 of German Application No.198 46 873.3, filed on Oct. 12, 1998. Applicants also claim priorityunder 35 U.S.C. §120 of PCT/EP99/07447, filed on Oct. 6 1999. Theinternational application under PCT article 21(2) was not published inEnglish.

BACKGROUND

The present invention relates to an elastic shaft coupling comprising atleast one torsion element having at least one elastomer body serving asa transmission element. Axial metallic connecting flanges are mounted ina fixed manner on said elastomer body on the input and output sidesparticularly by vulcanization

In conjunction with such shaft couplings comprising torsion elements,the torque is exclusively transmitted via one or a plurality ofelastomer bodies, which, as a rule, are high-quality coupling rubberbodies. Metallic connecting flanges in the form of disks areundetachably mounted on the axial face sides of the one or more rubberbodies for introducing the torque into said rubber body or bodies. Thebest joint is currently produced by vulcanization.

Under dynamic load, i.e. in the transmission of torques that arevariable in terms of time, as they are present, for example due totorque peaks in large diesel engines with low flywheel mass, thetransmission elements are subjected to torsion that is variable in termsof time as well. Due to such dynamic load, heat loss occurs in thecourse of deformation of the elastomer body as a result of internalfriction. Since the stressability of elastomer materials even with thehighest operational efficiency decreases with the rise in temperature,efficient measures are employed for cooling, i.e. for dissipating heatfrom the rubber body.

For cooling the core areas of the rubber bodies, which require specialattention in light of the fact that elastomer materials basically have arelatively low specific thermal conductivity, it is already known sincea long time to employ instead of a ring-shaped, through-extendingelastomer transmission element a plurality of segment-shaped torsionelements having connecting flange segments. Such a torsion element isknown, for example from DE 37 10 390 C2.

It is also known already from said DE 7 10 390 C2 to provide bothone-piece, ring-shaped and segment-shaped torsion elements with axialbreakthroughs extending axially through the connecting flanges, and theelastomer body with axial venting channels.

The cooling air, which flows in between the segments or through thebreakthroughs in the connecting flanges, provides in an advantageousmanner for effective air cooling of the rubber bodies, so that it waspossible to substantially increase the power density of such torsionelements. This, however, leads to particularly high loads acting on theelastomer/metal joint, i.e. the active vulcanized area of the rubberbody on the connecting flange. Particularly endangered with respect tothe formation of cracks in the rubber, or initial tearing of theelastomer/metal joint, are the edges of the connection area on theradial outer edges of the connection flange segments, or on the inneredges of breakthroughs, i.e. of venting openings in the connectingflanges.

For the purpose of preventing the formation of cracks and detachment inthe marginal zones or on the edges of the rubber/metal joint, it hasalready been proposed in AT 154 034 to round off the edges and to designthe rubber body in such a way that it extends around the face sides ofthe edges. A further development of said basic idea is specified in DE33 10 695 C2. Said document relates to torsion elements where the radialface edges of the connecting flange segments are provided with arounded-off profiling, around which the rubber body is drawn.

The measures according to the prior.art explained above offer theadvantage that the adhesion of the rubber body to the edge of therubber/metal connection area is enhanced. Another positive effect isthat the axial width of the rubber body in said marginal zones and thusthe active elastic length are increased. However, in light of the factthat the requirements that have to be satisfied with respect to powerdensity are constantly increasing, the limits of the measures specifiedabove have just about been reached in the meantime, because it has beenfound that under maximum load, bending stresses are exerted on theprojecting area of the rubber body in spite of the curved profiling ofthe edges. Furthermore, the active elastic length within the zone of theradial faces of the segments or in the cross section of thebreakthroughs in the connecting flange can be increased only by theaxial thickness of the material of the connecting flanges. This definesstress limits which, until the present time, cannot be exceeded.

SUMMARY

Now, the problem on which the present invention is based is to furtherdevelop torsion elements of the type specified above in that highertransmittable power densities become possible. Such optimization takesinto account particularly the special stress occurring within the areaof the faces of connection flange segments and along the edges of thebreakthroughs in the connecting flanges.

For solving said problem, the invention proposes that at least along theradially extending edges of the connecting flanges in the area where theelastomer body and the connecting flanges are joined, said edges beingformed are along the outer edges of the connecting flange segments,and/or on the inner edges of breakthroughs in the connecting flange, theconnecting flanges axially project outwards from the plane of theconnecting flange with respect to the elastomer body; and that theelastomer body is joined with the flanges along the arched area byvulcanization.

According to the invention, the connecting flanges are bent axiallyoutwards in those locations where the free edges of the rubber/metalconnection interface extend radially and are consequently exposed tospecial loads. This applies in particular to the inner edges ofbreakthroughs, i.e. of venting openings provided in the connectingflange, or, in conjunction with segmented connecting flanges, to theradial outer edges of the connecting flange segments. Owing to theoutwardly projecting edge zone as defined by the invention, the areawhere the rubber and the metal are joined by vulcanization is widened inthe axial direction beyond the axial width of the connecting flange.

For practically implementing the design as defined by the invention, itis possible also to bend the plate-like connecting flanges axiallyoutwards along the edges, or, as an alternative, to form an axiallyoutwards projecting bead along the edges by molding. The last-mentionedembodiment is particularly advantageous if the connecting flanges or theconnecting flange segments are manufactured from cast steel.

An important advantage of the invention lies in the fact that on the onehand, the area of adhesion, i.e. the area of vulcanization within theedge zone, is enlarged irrespective of the thickness of the material ofthe connecting flanges in the axial direction. The force by which therubber body is held on the connecting flange is absolutely increased, onthe one hand. On the other hand, the bending stress caused by thegreater radius of the curvature of the projecting or curved edges issubstantially reduced vis-à-vis the relatively narrow edge zones foundin the prior art, which optimizes the introduction of force into therubber body.

Another advantageous effect of the invention is that the active elasticlength of the rubber body between the edge zones projecting as definedby the invention is substantially increased, to a degree higher than itwould basically be possible in the prior art. In the prior art, therubber body theoretically can be widened only by the axial thickness ofthe material of the connecting flanges, whereas this limitation isovercome in conjunction with the invention because the edges of theprojecting edge zones can be readily bent outwards by multiple times theamount of such axial thickness, which naturally leads to a wideningwithin said area correspondingly. This translates into a decrease in thestress values maximally occurring during operation. In cooperation withthe enlarged area of adhesion as defined by the invention and explainedabove, a substantial increase of the power density is achievable.

The embodiment as defined by the invention is equally applicable to thedesign of the radial edges of connecting flange segments as well withinthe breakthrough arranged in the connecting flanges. In connection withthe breakthroughs, this is possible irrespectively of whether they arefilled with rubber material, or whether such breakthroughs are adjoinedby venting channels in the rubber body.

In a preferred embodiment of the invention, the torsion element hasventing openings axially extending through the connecting flanges andthe elastomer body. The interior of the elastomer body is effectivelycooled by air flowing through the axial venting channels adjoining theaxial breakthroughs in the connecting flange. Owing to the fact that theventing openings are arranged within breakthroughs provided as definedby the invention, i.e. provided with projecting or beaded edges,enhanced adhesion is obtained in the edge zones of the rubber/metaljoint located there as well.

According to a further development of the invention, provision is madethat the elastomer body has radial venting channels. This makes itpossible, furthermore, that the radial venting channels can be connectedwith the aforementioned axial venting channels. In this way, the torsionelements are structured in the way of a radial compressor. Duringrotation, ambient air is aspirated via the axial openings due tocentrifugal forces, and discharged into the outside by way of the radialventing channels across the periphery of the elastomer elements. Theconstant flow of air results in particularly effective cooling.

The radial venting channels are usefully open radially outwards. Thismeans that they can be closed radially inwards. Active rubber materialtherefore remains standing in the interior for transmitting the torque.

In conjunction with embodiments having radial venting openings, it isparticularly advantageous if the connecting flanges have breakthroughslocated within the peripheral zone between said radial venting openings.Such breakthroughs do not change into venting channels but are filledwith rubber material. By virtue of the embodiment as defined by theinvention, comprising edge zones that are axially projecting outwards,the elastic length is increased within the zone of the breakthroughs, onthe one hand, and additional adhesion and stability of the rubber bodybetween the radial venting channels are made available on the other.

BRIEF DESCRIPTION OF THE DRAWINGS

Other objects and features of the present invention will become apparentfrom the following detailed destiption considered in connection with theaccompanying drawings. It is to be understood, however, that thedrawings are designed as an illustration only and not as a definition ofthe limits of the invention.

In the drawings, wherein similar reference characters denot similarelements throughout the several views:

FIG. 1 is an axial view of a torsion element segment as defined by theinvention.

FIG. 2 shows a radial section C-D according to FIG. 1.

FIG. 3 shows a radial half section C-A according to FIG. 1.

FIG. 4 is a partial view of a section in the peripheral directionaccording to FIG. 1 within the reference radius R.

FIG. 5 shows an axial section through the torsion element segmentaccording to FIG. 1; and

FIG. 6 is a radial partial view from the outside.

DETAILED DESCRIPTION

FIG. 1 shows an axial view of a segment-shaped torsion element asdefined by the invention, which is denoted in FIG. 1 by referencenumeral 1. Said view substantially shows an axial top view of one of thetwo consecutively arranged, equally structured, quarter circle-shapedconnecting flange segments 2.

In a complete shaft coupling, a total of four of the shown torsionelements 1 are assembled in such a way that the circular connectionflange segments 2 form a connecting flange that has a circular shapeoverall. Between the radial edges of the connecting flange segments 2,the connecting flanges on the input and output sides each haveconsequently a total of four breakthroughs.

In the radial edge zones 2 a of the connecting flange segments 2, theconnecting flange 2 as defined by the invention is projecting outwards,thus in the present case in the direction of the viewer, i.e. it is bentor beaded up along the edge zone 2 a.

Furthermore, the connecting flange segment 2 has a total of fivebreakthroughs 3, which are through-extending and have an about U-shapedcontour. Said breakthroughs are bent or beaded upwards in the directionof the viewer like the aforementioned edge zones 2 a as well.

The circular, axially through-extending venting openings 4 are locatedon a graduated circle disposed on the inside. Said venting openings maybe provided with edge zones projecting as defined by the invention aswell, which, however, has not been realized in the embodiment shown.

Reference numeral 5 denotes a rubber body serving as the transmissionelement. Said rubber body is joined with the successive connectingflange segments 2 by vulcanization. Said rubber body 5 is segment-shapedas well and, in the present representation, is covered for the most partby the connecting flange segment 2. The rubber body is visible only inthe areas drawn around over the edge zones, as well as through thebreakthroughs 3, which is indicated by the reference numeral (5) set inbrackets. The venting openings 4 axially penetrate the rubber body 5 aswell.

FIG. 2 shows a radial section through the torsion element 1 according toFIG. 1. Identical components are denoted by the same reference numeralsas in FIG. 1.

It is particularly obvious from FIG. 2 how the edges 3 a of thebreakthroughs 3 are projecting outwards or are bent up. The rubber body5, which fills the breakthroughs 3, follows the outwardly projectingarea and is fixed there on the connecting flange segment 2 byvulcanization as well.

Said representation also shows that the venting openings 4 feed into theradial venting channels 6 in the rubber body 5, which are open onlyoutwards toward the periphery and closed toward the inside.

FIG. 3 shows a half section in the same representation as in FIG. 2;however, said half section is disposed in the peripheral area betweenthe breakthroughs 3. In the representation in FIG. 3, the edges 3 a,which are projecting outwards like a collar, are visibly indicated aswell.

FIG. 4 shows a partial view of a section in the peripheral direction inthe reference radius R through the radial edge zones 2 a of theconnecting flange segment 2. This shows with special clarity how theconnecting flange segment 2 is axially projecting outwards or bent upfrom the plane of the connecting flange in the edge zone 2 a. The rubberbody 5 extends around said edge zones 2 a in the peripheral direction.In the present case, the bent-up areas 2 a could be referred to also asbead-like moldings.

It becomes obvious from FIG. 4 that compared with the inner zone, whichis disposed between the inner sides of the connecting flange segments 2,the effective elastic length of the rubber body 22 is distinctlyincreased in the marginal area 2 a.

FIG. 5 shows an axial section through the torsion element 1 according toFIG. 1 by the same view, which shows the arrangement of the individualfunctional elements with special clarity.

FIG. 6 shows a radial view of the venting channels 6 from the outside.Their oval cross section, which is narrowing radially inwards, can beclearly recognized in said view.

The advantages according to the invention consist in that the rubberbody 5, owing to the outwardly bent up or beaded up edges 2 a and 3 a,has the greater active vulcanization area there, as if the butt edgeswere only cut off there in a plane manner as it is the case in the priorart. The elastic length, i.e. the axial width of the rubber body 5, iseffectively increased in said areas as well. This means that therelative stresses attacking on the rubber-metal transition area areadditionally reduced.

This means that the joint of the rubber body 5 with the. connectingflange segment 2 can be stressed to a particularly high degree both inthe radial face areas of the torsion element 1 and in the breakthroughs3. The risk of detachment or formation of cracks is thus substantiallyreduced. This permits in increase in the transmittable power density.

Effective cooling of the rubber body 5 is ensured on account of the factthat because of the centrifugal forces occurring during rotation, coolair is aspirated through the axial venting openings 4 and radiallydischarged to the outside through the radial venting channels 6.

The increase in the elastic length effectively obtained within the zoneof the breakthroughs 3 provides the shaft coupling with optimalproperties of elasticity.

Accordingly, while only a few embodiments of the present invention havebeen shown and described, it is obvious that many changes andmodifications may be made thereunto without departing from the spiritand scope of the invention.

What is claimed is:
 1. An elastic shaft coupling comprising at least onetorsion element serving as a transmission element, each torsion elementcomprising: at least one elastomer body; at least one axial metallicconnecting flange mounted in a fixed manner via vulcanization on inputand output sides of said at least one elastomer body and said at leastone connecting flange having radially extending edges; and a pluralityof breakthroughs that extend through said at least one connectingflange, wherein said plurality of breakthroughs have inner edges;wherein said radially extending edges and said inner edges of saidplurality of breakthroughs project axially outward in a curved mannerfrom a plane of said at least one connecting flange with respect to saidat least one elastomer body; and wherein said at least one elastomerbody is connected to said at least one connecting flange along saidoutwardly curved edge regions of said at least one connecting flange. 2.The shaft coupling according to claim 1, wherein said inner edges ofsaid plurality of breakthroughs and said radially extending edges ofsaid at least one connecting flange have beads pointing up.
 3. The shaftcoupling according to claim 1, wherein a bead axially projecting beyondthe outer surface of said at least one connecting flange is shaped bymolding along said inner edges of said plurality of breakthroughs andsaid radially extending edges of said at least one connecting flange. 4.The shaft coupling according to claim 1, wherein each torsion elementfurther comprises axial venting openings that extend through said atleast one connecting flange and said at least one elastomer body.
 5. Theshaft coupling according to claim 4, wherein said axial venting openingsare disposed within said plurality breakthroughs.
 6. The shaft couplingaccording to claim 1, wherein said at least one elastomer body comprisesradial venting channels.
 7. The shaft coupling according to claim 6,wherein said radial venting channels open radially outwards.
 8. Theshaft coupling according to claim 6, wherein said plurality ofbreakthroughs are disposed peripherally between said radial ventingchannels.
 9. The shaft coupling according to claim 6, wherein saidradial venting channels and said axial venting openings of said at leastone elastomer body are connected with each other.